H11 kinase is the eukaryotic homologue of ICP10 protein kinase, a Ras-GAP kinase from Herpes Simplex required for virus growth. In normal tissues, H11 kinase expression is restricted to the heart and skeletal muscle. Although its function remains unknown, H11 kinase probably participates in mechanisms of cell growth because its induction in non-muscular cells promotes transformation into cancer cells. Putative interactions include the nuclear casein kinase II (NUCKS II), a stimulator of cell growth, the protein HSP27, a stimulator of cell survival, and the nucleosome assembly protein-1 (NAP-l), a stimulator of cell proliferation. By subtractive hybridization, we unexpectedly found that H11 kinase transcript and protein are upregulated in large mammalian models of reversible ischemia/reperfusion and chronic left ventricular hypertrophy. Our preliminary data show that overexpression of H11 kinase in isolated cardiac myocytes promotes cell growth. A cardiac-specific transgenic mouse has been generated, which confirms that overexpression of H11 kinase induces cardiac hypertrophy and protects against cell death during ischemia/reperfusion in vivo. Based on these observations, the overall goal of this proposal is to determine the physiological role, signaling mechanisms and functional importance of H11 kinase in the myocardium. The first specific aim is to determine in vivo the functional and genomic effects of H11 kinase overexpression in a cardiac-specific transgenic mouse model submitted to transverse aortic banding or ischemia/reperfusion. We hypothesize that H11 kinase overexpression in transgenic mice will decrease irreversible cellular damage in hypertrophied and ischemic hearts. The second aim is to determine the signaling pathways in which H11 kinase is integrated. We hypothesize that H11 kinase promotes cardiac growth and survival by stimulating NUCKS II, HSP27 and NAP-l, but that other unexpected proteins might interact as well. The third aim is to show, both in vitro with a dominant negative and in vivo in a knock-out model, that H11 kinase represents an essential pathway of cardiac growth and survival. We hypothesize that the tissue-restricted expression of H11 kinase underlies a specific signaling pathway that is not dispensable for normal cardiac cell growth. These experiments will unravel novel mechanisms and signaling pathways of cardiac growth, which may result in new therapeutic avenues for both ischemic heart disease and heart failure.